Add GeoIP support for unique IP aggregation

- Introduced GeoIP configuration options in config.example.yaml to enable geolocation lookups for the /api/agg/unique-ips endpoint.
- Updated the aggregate handler to include optional GeoIP data in responses, enriching unique IP information with country and city details, as well as ASN data if available.
- Enhanced documentation in AGGREGATE.md and README.md to reflect the new GeoIP functionality and its usage.
- Added a dependency on the geoip2-golang library in go.mod for GeoIP lookups.
- Modified tests to accommodate the new GeoIP integration in the aggregate handler.

cmd/gateway/main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"context"
 	"log/slog"
+	"net"
 	"net/http"
 	"os"
 	"os/signal"
@@ -10,6 +11,7 @@ import (
 	"time"
 
 	"github.com/telemt/telemt-api/internal/config"
+	"github.com/telemt/telemt-api/internal/geoip"
 	"github.com/telemt/telemt-api/internal/server"
 )
 
@@ -31,7 +33,20 @@ func main() {
 		os.Exit(1)
 	}
 
-	gw, err := server.NewGateway(parsed, log)
+	geoDown := &http.Client{
+		Transport: &http.Transport{
+			DialContext:           (&net.Dialer{Timeout: 30 * time.Second}).DialContext,
+			ResponseHeaderTimeout: 5 * time.Minute,
+		},
+		Timeout: 15 * time.Minute,
+	}
+	geo, err := geoip.FromConfig(parsed.Config.GeoIP, geoDown, log)
+	if err != nil {
+		log.Error("geoip init failed", "err", err)
+		os.Exit(1)
+	}
+
+	gw, err := server.NewGateway(parsed, log, geo)
 	if err != nil {
 		log.Error("gateway init failed", "err", err)
 		os.Exit(1)